Process for vulcanizing rubber and products obtained thereby



Patented Feb. 8, 1927;

UNITED STATES PATENT OFFICE.

MORRIS L. WEISS, 0F NEWARK, NEW JERSEY. ASSIGNOR TO DOVAN CHEMICAL COR-POBATION, OF NEW YORK N. Y., A CORPORATION OF NEW YORK.

PROCESS FOR VULCANIZING RUBBER AND PRODUCTS OBTAINED THEREBY.

No Drawing. Application filed July 29, 1925, Serial No. 46,876. RenewedNovember 5, 1826.

This invention relates to processes for vulcanizing rubber and similarmaterials and to the products obtained thereby, and is more particularlydirected to acceleration of vulcanization by a class of substitutedguanidines.

In my previous Patent No. 1,411,231 granted March 28, 1922, I havedescribed the formula NHCJI; (j NcsHl N HCaH;

but I have found that this material when (ompoundcd in a formula similarto that employed with diphcnyl guunidine and diorlho tolyl guiuidinc isa relatively weak accelerator.

One object of the present invention, accordingly, is to provide astrong, stable, non-toxic accelerator of vulcanization of thetri-snbslituted type of compound heretofore regarded as only a weakaccelerator.

Another object is to provide a simple process of vulcanization employingsuch an accclerator and to produce a series of useful product's thereby.

According to the present invention I have found that unsymmetricaltri-snbstitutcd guanidincs having the formula Nun un: where R is an arylradical constitute a group of valuable accelerators of vulcanization. Itwill be noted in this formula that an imid group NH is present, whichaccording to my observations is largely responsible for three of thefour the accelerating -properties of this material.

It will be noted in the formula for the symmetrical tri-substitutcdguanidine that the iniid group is missing. As soon as this imid groupdisappears apparently the accelerating power is greatly reduced so thatthe substance is the accelerators diphenyl guanidine and diorlho tolylguanidine. Both of the latter contain imid groups, and in the case ofeach it has been observed that its peculiar'accclerating characteristicsare due to the presonce of this group.

The invention accordingly comprises combining rubber with a substitutedguanidine including an imid group and having at least remaininghydrogens substitutcd by aryl groups. e. g. an unsymmetrical tri-arylsubstituted gguanidine as a vulcanizing ingredient and vulcanizing therubher. In using izing ingredient I mean that the unsymno longer in thesame class as the expression as a Vulcan-v metrical tri-substitutedguanidine is a. component part of a combination or mixture wh ch 15 usedto eli'ect vulcanization and which ordinarily includes sulphur andmayand preferably does include zinc oxide or equivalent thereof.

In carrying out the invention in its preferred form 100 ounds ofrubber-first latex crepe-5U poun s of zinc oxide. 3 pounds of sulphurand 0.75 pounds of beta triphenyl substituted guanidine having the,fUllllNltl.

NGlhlh (alpha) N(CHa)2 (beta) are combined preferably in the usualmannor by milling. The compound is placed in a mold and heated at 40pounds per square inch steam pressure for 60 minutes at the end of whichtime a satisfactory vulcaniza lion is secured.

I'give below atable showing results which 1 have obtained u on the samelot of rubber and other ingrec ients in which, however, the acceleratorbeta tri-phenyl guanidine is substituted by he same amount ofsymmetrical tri-phenyl guanidine the same amount of diphcnyl guanidineand the ,same amount of diortho tolyl guanidine with the resultssecu'red upon vulcanization for 30, and

guauidiuc, an unsymmetrical l-ri- Beta triphenyl guanidine is thus shownto be a strong accelerator. It. is non-toxic and stable. The recess ofvulcanization emplpiying it is sim 1e and eflicient.

he compoun used in the above was as follows: 7

100 lbs. 1st latex ere e, 50 lbs. XX zinc oxide, 3 lbs. sulphur, b.accelerator.

Unsymmetrical or eta trihe%l guanidine is prepared according to V. eithand 13. Schroeder, Berichte der Deutschcn Chem. GcselL, vol. 8, page 294as follows: One mol. cyananilide or henylcyanamide, C,H,NH.CN, is mixedwit an excess over one mol. of diphcnyl amine hydrochloride,

Cd] un---ncn Cilia and heated slowly. At about 80 C. the reaction setsin, as evidenced by a quick rise .in temperature. The flame is removedas the temperature risesabove 100 C. and the mixture is brought to about105 C. The heating is then continued at 105 C. for about 2 hrs. The temerature is then raised to about 125? C. amFkept there for 15 minutes.The reaction product, a viscous mass, is then boiled up with waterseveral times and filtered. The filtrate is then poured into a dilutecaustic soda solution with stirring and the guanidine first )recipitutesout as a mmy mass but soon eco'mes crystalline. This is filtered off,washed and dried. M. P. 127 C. On recrystallizatiop from alcohol,isometric plates are obtained. M. P. 131 U.

The product is easily soluble in alcohol and ether, insoluble in waterand forms easily .soluble salts. The reaction is as follows:

no According to Weith 8: Schroeder, beta triphenyl Euauidine is adisubstituted guanidme an contains an imid NH group, as

shown by the following tests:-

Beta tri-phenyl giianidine when heated with concentrated hydrochloricacid in .a sealed tube 2602T0 C. evolves a gas. On opening the tube .itwas found to be CO with baryta water. The contents of the tubeuponcxtraction with water produced an insoluble substance. Thisinsoluble substance was extracted with ether and proved to be diphcnylamine M. 1. 54 C. The water soluble material upon being shaken withether, separated and evaporated produced a residue from the etherextract which proved to be aniline hydrochloride. The water extractcontained ammonium chloride.

Symmetrical' tri-phenyl guanidine when treated similarly gives onlycarbon dioxide and aniline.

In the formula NHR -NH \pnn R has been substituted by the phenyl groupCJI, in rovidin the material given in tilt preferre exampe above, betatri-phenyl guanidine. Other aryl radicals such as tolyl, xylyl, cymyl,cumyl, na hthyl or mixtures thereof may be employe to re lace one ormore of the phenyl groups. It ias been found furthermore that zinc oxidemay be omitted if desired, although it is a valuable vulcanizing inedient in the process and the product. t has been found that thetemperature and time employed in vulcani zation may be considerablyvaried. The temperatures at which rapid acceleration occurs are,however, above the usuultemperuturc at which rubber is milled andconsequently the accelerator shows substantially no tendency toburnprevulcunize-on the mill.

It has been found however, that materials of the t pe herein discussed,particularly beta trip \enylguanidine provide a practical accelerationat temperatures lower than those employed'with diphenylguanidine toproduce like results. In other words, at 20 pounds per square inch steampressure, beta triphenylguanidine gives a vulcanized rubher having amuch higher tensile strength than does diphenylguanidine. The followingcomparative results have been obtained by tests at 20 pounds per squareinch steam pressure on the same rubber compound containing pounds ofrubber, 3 pounds of sulphur, 50 pounds of zinc oxide and 0.75 pounds ofaccelerator 45 minutes 00 minutes tensile along. tonal Accelerator usedI! on;

l.850lb6. 855% 729 lbs. 765% 2,057lhs.820%

1.5mm. sa(% 2,407lhs. mm,

2,015 lbs.835%

The fact that a higher tensile strength at a lower steam pressure issecured by using betatriph'enylguanidine when compared withdiphenylgua'mdine as indicated by the above of a tire and the tread isthen applied an the article so formed is placed in a mold and heated,the heat penetrates to the interior plies relatively slowly and for j aconsiderable portion of a vulcanizing pe' riod these interior plies areat a substantially lower temperature than the tread. Under thesecircumstances it is advisable to have an accelerator which acceleratesat a relativelyhigh temperature, say, pounds per square inch steampressure in the tread, and an accelerator which accelerates at a lowertemperature, say, 20 pounds per square inch in the friction stock, sothat it is evident that betatriphenylguanidine on account of its abilityto accelerate at the lower temperature to produce high tensile strengthsis particularly applicable to friction stocks.

It will be observed that in the formula,

and beta positions have been substituted and may be termed alpha phenylbeta diphenyl guanidine or otherwim for conciseness, beta triphenylguanidine. If the fourth hydrogen appearin 'in the alpha position aboveis substituted by a pheny group a tetra substituted guanidine having animid group is obtained which possesses similar accelerating propertiesto the beta triphenyl guanidine described in the preferred example. Iwill be understood that when I use the expression in the claims havingat least three hydrogens in the alpha and beta positions substituted, Iintend to include such tetra substituted guanidine.

As many apparently Widely different em- .bodiments of this invention maybe made without departing from the scope thereof, it is to be understoodthat, I do not intend to limit myself to the specific embodimentof theinvention hereindescribed, except as indicated in the appended claims.

That I claim is:

1. A process of treating rubber or similar material which comprisescombining with the rubber an unsymmetrical tri-substituted guanidinehaving the-formula xmz rin as a vulcanizing ingredient and vulcanizingthe rubber.

2. A process of treating rubber or similar material which comprisescombining with the rubber an unsymmetrical tri-substituted guanidinehaving the formula Nncan I-NH 0HI)i as a vulcanizing ingredient, andvulcanizing the rubber.

3. A. process of treating rubber or similar material which comprisescombining with the rubber sulphur, an unsymmetrical trisubstitutedguani'dine having the formula Nncun =Nn i t ih and vulcanizing therubber.

4. A recess of treating rubber or similar materia which comprises'combining with the rubber sulphur, a zinc compound, such as zinc oxide,an unsymmetrical tri-substit'uted mmnidine having the forumla andvulcanizing the rubber.

5. Aprocess of treating rubber or similar material which comprisescombining with the rubber a substituted'guanidine having an imid groupin which at least three of the four remaining hydrogens inthe alpha andbeta positions are substituted, as a vulcanizing ingredient andvulcanizin the rubber.

6. A process of treating rub r or similar material which comprisescombining with approximately 100 unds of rubber, approximately poun s ofzinc oxide, approximately 3 pounds of sulphur and npproximately 0.75pounds of beta tri-phenyl gunnidine, and vulcanizing the mlxture in amold at approximately 40 pounds per square inch steam pressure for 45minutes.

7. As a new product, a vulcanized rubber derived from rubber combinedwith 9. As a new pro not, a vulcanized rubber derived from rubbercombined with sulphur and NHCcHs 04m 10. As a new roduot, a vulcanizedrubber derived from ru ber combined with sulphur, a zinc compound, suchas Zinc'oXide, and an unsymmetrlcal tri-substitubed guanidine hav- 5 'mgth formula.

NBC/H:

compound of zinc, sulphur and beta triphenyl guanidine, and vulcanizingthe mixture.

12. As a new product, a vulcanized rubber, derived from rubber combinedwith acompound of Zing sulphur, and beta tri pheuyl guanidine.

Signed at New York, N. Y., this 28th day of July, 1925.

MORRIS L. WEISS.

10. As a new roduct, e vulcanized rubber derived from ru ber combinedwith sulphur, a zinc com und, such as zinc oxide, and an unsymmetricaltri-substitutcd guanidine having th formula derived ,from rubbercombined with a com- 15 NHCOBI pound of zinc, sulphur, and beta triphenyl guanidine. Signed at New York, N. Y., this 28th day l 2!. 11. Aprocess of treating rubber or similar of July 19 material whichcomprises combining rubber MORRIS L. WEISS.

Oertilcate of Correction.

Potent No. 1,616,936, granted February 8, 1927, to

MORRIS L. WEISS.

It is hereby certified that error appears in the printed specificationof the abovementioned potent requiring correction as follows: Page 1,after line 87, strike out the formula. and insert instead /NH e t mm) OHH Momm s) page 3, after line 127, claim 9, strike out the formula andinsert instead /NTK ent and that the said Letters Patent should be readwith this correction therein the! the same mav conform to the record ofthe case in the Patent Office.

Signed and sealed this 1st day of March, A. D. 1927.

[mm] M. J. MOORE,

Acting Commissioner of PM.

Gertllcate of Correction.

Potent No. 1,615386, granted February 8, 1927, to

MORRIS L, WEISS. It is hereby oorfifioq 13bit error oppears in thegrintod s 'fioation of abovementlonod nt correchon as follows: age 1, ar hne 87, stnke out the formula. moat) Am' n (can). om) pigs 3, otterline 127., claim 9, strika out the formula and insert instead HE GE: 04

and thlt the said Lotters Patent should be read with this correctiontheroin that the some ma conform to the record of the case inthe PatentOfice.

Sig-notion sealed this 1st day of March, A. D. 1927.

[mu-.1 M. J. MOORE,

Acting Commiuiomr of PM.

